use nom::branch::alt;
use nom::combinator::eof;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many1;
use nom::multi::many_till;
use nom::sequence::tuple;

use super::element_parser::detect_element;
use super::lesser_element::Paragraph;
use super::org_source::OrgSource;
use super::util::blank_line;
use super::util::get_consumed;
use super::Context;
use crate::error::Res;
use crate::parser::exiting::ExitClass;
use crate::parser::object_parser::standard_set_object;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_context::ExitMatcherNode;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::start_of_line;

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub fn paragraph<'r, 's>(
    context: Context<'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, Paragraph<'s>> {
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Gamma,
            exit_matcher: &paragraph_end,
        }));
    let standard_set_object_matcher = parser_with_context!(standard_set_object)(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);

    let (remaining, (children, _exit_contents)) = verify(
        many_till(standard_set_object_matcher, exit_matcher),
        |(children, _exit_contents)| !children.is_empty(),
    )(input)?;

    // Not checking parent exit matcher because if there are any children matched then we have a valid paragraph.

    let source = get_consumed(input, remaining);

    Ok((
        remaining,
        Paragraph {
            source: source.into(),
            children,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn paragraph_end<'r, 's>(
    context: Context<'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    let non_paragraph_element_matcher = parser_with_context!(detect_element(false))(context);
    alt((
        recognize(tuple((start_of_line, many1(blank_line)))),
        recognize(non_paragraph_element_matcher),
        eof,
    ))(input)
}

#[cfg(test)]
mod tests {
    use crate::parser::element_parser::element;
    use crate::parser::org_source::OrgSource;
    use crate::parser::parser_context::ContextTree;
    use crate::parser::parser_with_context::parser_with_context;
    use crate::parser::source::Source;

    #[test]
    fn two_paragraphs() {
        let input = OrgSource::new("foo bar baz\n\nlorem ipsum");
        let initial_context: ContextTree<'_, '_> = ContextTree::new();
        let paragraph_matcher = parser_with_context!(element(true))(&initial_context);
        let (remaining, first_paragraph) = paragraph_matcher(input).expect("Parse first paragraph");
        let (remaining, second_paragraph) =
            paragraph_matcher(remaining).expect("Parse second paragraph.");
        assert_eq!(Into::<&str>::into(remaining), "");
        assert_eq!(first_paragraph.get_source(), "foo bar baz\n\n");
        assert_eq!(second_paragraph.get_source(), "lorem ipsum");
    }
}